1. Field of the Invention
The present invention relates to a rotary connector having a pair of housings which constitute a fixed member and a movable member, respectively, and which are interconnected electrically through a flexible cable such as a flat cable or the like. Particularly, the invention is concerned with a lock mechanism for locking or unlocking a free rotation of the movable member.
2. Description of the Prior Art
A rotary connector of this type is incorporated in an automobile steering system and is used as a conducting means for, for example, an air bag circuit which connects between the steering wheel and the body of the automobile. In this case, it is necessary to mount the rotary connector in such a manner that the movable member can rotate in both directions to about the same degree from a neutral position of the steering wheel. To meet this requirement, the rotary connector is provided with an alignment mechanism for aligning the fixed member and the movable member to a neutral position of rotation and a lock mechanism for maintaining such neutral state until the rotary connector is mounted into the steering system.
The former alignment mechanism is constituted by providing one of the fixed member and the movable member with a rotating member having a gear and providing the other with an engaging member for engagement with the gear of the rotating member. At every rotation of the movable member, the gear comes into engagement with the engaging member and rotate by a predetermined angle, so that the neutral position is attained when the a specific tooth of the gear is in a predetermined position and when the movable member is in a predetermined position relative to the fixed member. In view of this point, a mark is provided on the specific tooth of the gear and also on a member which supports the gear, and by alignment of these marks at the time of mounting the rotary connector to the steering system, the rotary connector can be mounted in the neutral position of the movable member relative to the fixed member.
As the latter lock mechanism referred to above there have been proposed various types, but generally known is the type using a lock member which can be mounted and removed with respect to the rotary connector. According to the construction of this known type, the lock member is fixed to either the movable member or the fixed member with a set-screw and is retained to the other. Since the free rotation of the movable member is prevented by the lock member, it is possible to maintain the neutral state of the movable member and the fixed member which have been aligned by the foregoing alignment mechanism. Then, by loosening the set-screw and removing the lock member from the rotary connector at the time of mounting the rotary connector to the steering system, the locked state between the movable member and the fixed member is released, so that the movable member becomes rotatable freely.
In the case of the above conventional lock mechanism, it is necessary to loosen the set-screw and remove the lock member from the rotary connector at the time the locked state is released. Consequently, the set-screw and the lock member are apt to become separated from each other and hence it is required to pay close attention to the handling of those two parts. Particularly, since the set-screw is rotated with a jig such as a screwdriver or the like, it is apt to fall off in the course of removal of the lock member from the rotary connector. Once the set-screw falls off, it may stay within the steering system and generate a noise during running of the automobile or may cause short-circuit of peripheral circuits because the set-screw is electrically conductive. Further, at the production stage of the rotary connector and after alignment of the movable member and the fixed member to the neutral state by using the foregoing alignment mechanism, it is necessary to insert the set-screw into a hole of the lock member and tighten it into a threaded hole formed in the movable member or the fixed member. However, since the threaded hole is covered with the lock member, the hole-threaded hole aligning work is troublesome, and thus also in this point there has been a difficulty in the assembling work.
As disclosed in U.S. Pat. No. 5,248,260, there has been proposed a lock member integral with a plurality of stopper pieces for preventing the falling-off of the set-screw. However, since the stopper pieces are each of an undercut shape, there arise other problems such that the cost of a mold for molding the lock member rises to a great extent and that the stopper pieces are each an obstacle to the engagement of a jig with the set-screw.